Treatment of cellulosic materials and to the production of cellulose esters and cellulose ester products therefrom



Patented May 23, 1933 career HENRY DREYFUS, OF LONDON, ENGLAND TREATMENT F CELLULOSIC MATERIALS AND TO PR-QD'UCTIGN 01 CELLULOSE ESTERS AND 'UELLULOSE PRODUCTS THEREFEOE' No Drawing. Application filed December 24, 1928, Serial No. 328,396, and in Great Britain January 14, 1928.

This invention relates to the treatment 01"? cellulosic materials for the purpose of rendering them more reactive for esterilication and especially acetylation and also to the 5 production of cellulose acetates or other cellulose esters from the materials so treated.

I have now found that cellulosic materials may be rendered more reactive towards acctlation or other esterification by a treatment with hydrochloric, hydrobromic or hydriodic acid or with mixtures of such hydrohalide acids or with mixtures of such hydrohalide acids with organic acids, more especially lower aliphatic acids such as formic or acetic acid.

quantity of hydrohalide acid used in the pretreatment should not exceed one half the weightof the cellulose and should prefen ably not be less than 2% thereof and is most advantageously in the neighbourhood oi 510%' {corresponding to about 1"30% of commercial acid in the case of hydrochloric acid) ,though very good results are obtainable with quantities of 20% or even on the weight of the cellulose.

The hydrohalide acid may, if desired, be employed as a but is preferably dissolved in or diluted with a liquid, for example water. alternately, or in addition, the hydrohalide acid may be mixed or dissolved in an organic acid, particularly formic or acetic acid. Here again the hydrochloric acid or other hydrohalide acid is reterably dissolved in water and applied together with the formic, acetic or other acid. The use of acetic acic in conjunction with the hydrohalide acid oilers A articular advantages in that it can be employed in a subsequent acetylation oi the prel l celluose. For example the cellulose 40 may be pretreated with hydrochloric acid mixed wit n acetic acid in any desired quantity up to that required in the subsequent acetyletion and, after die pretreatment, a catalyst may be added together with acetic anhydride and it required, further acetic acid and the acetylation carried out directly.

As initial materials cotton (in either the mercerized or the non-merceriI Ied term) or other celluloses or near conversion products thereoi or other cellulosic materials may be employed. The cellulosic material used may which the lignin, pentosan, resin and like constituents have been substantially removed, "for example sulphite pulp, soda pulp, or sulphate pulp may be employed, but in the case of such materials the pretreatmentprocesses ot the present inven ion are preferably comhined witn and follow an alkaline purifying treatment. In such a method of treatment the wood pulp or the like is first subjected to an alkaline purifying treatment in the manner described in my U. S. Patent No. 1,711,110 dated April 30, 1929, for example with caustic alkali of low concentration, such as 3% or under, with heating; or boili g, or with *austic alkali of higher concentration, such as 540% or more, in the cold or with only slight heating, and then subjected to hydrohalide acid treatment in substitution for the organic acid treatment of the said U, S. Patent No. 1,711,110 dated April 30, 1929.

in conducting the pretreatment with l1y-;

drohalide acids in the liquid form, the acids may be distributed evenly over th cellulosic mate im, for inst by spraying the cellulose in a drum or rxer the .cellulosic materialbeing turned itroni t no to time it neces-- sary to ensure uniform impregnation. The collulosic material is then allowed to stand until a product capable of rapid esterilication is obtained, for example for 1 to 2 up to 12 or hours or more. The pretreatment may be carried out with gaseous hydrohalide acids, preferably in admixture with vapours of organi acids.

The time the pretreatment Vawith the o the cellulosic mate-- rial, the concentration of the pretreating agent or agents, the temperature at which the cellulosic material maintained, and the degree of reactivity required in the product. The treatment is preferably carried out at or dinary temperatures but may, ii desired, be accelerated by the use of somewhat increased temperatures.

The use of higher temperatures which would result in disintegration of the cellulose must be avoided. Similarly large quantities of hydrohalide acid must not be used. The quantity of hydrohalide acid should not exceed (calculated as hydrogen halide) of the weight of the cellulose and is preferably much less than this.

The subsequent acetylation or esterification of the cellulosic materials thus treated may be carried out by any suitable process. If the hydrohalide acid used in the pretreatment be not required or be required in smaller quantity in the acetylation or esterification, it may be wholly or partially neutralized, for example by addition of sodium or other acetate. Formic acid when employed in conjunction with hydrohalide acid in the pretreatment should, except when used in comparatively small quantities (see prior U. S. application S. No. 162,218 dated 19th J anuar 1927), be removed or substantially removed before acetylation with acetic anhydride as it reacts therewith. Any acetic acid employed in the pretreatment may remain in the cellulosic material to act as part of the esterifying mixture in the subsequent esterilication.

The process of pretreatment according to the present invention offers the greatest advantages when the subsequent acetylation or esterification is carried out according to the processes described in my prior U. S. application S. No. 301,927 dated 24th August 1928, 321,750 dated 24th November 1928 and 321,751 dated 24th November, 1928.

These specifications describe acetylation or esterification in presence of halides of iron, manganese, cobalt, nickel or copper in conjunction with a hydrohalide acid, each being present in a quantity not less than 2% on the cellulose; (b) ferric halide without hydrohalide acid; and (c) stannic halide with or without hydrohalide acid.

In acetylating or esterifying according to the processes described in my said prior applications, the hydrohalide acid used in the pretreatment need not be removed and it is therefore possible to proceed directly from the pretreatment to the esterification of the cellulose. If the hydrohalide acid be required in the acetylation or esterification the metal or other halide to be used in conjunction therewith, together with any additional hydrohalide acid if required, may be added to the pretreated cellulose separately or together with the acetylating or esterifying agent. When the acetylating or esterifying agent is to be added together with the halide salt, the latter may, if desired, be formed in situ in the acetylatiug or esterifying mixture. Instead of adding the halide salt as such, a substance such as ferric oxide or ferric acetate may be used so as to form the required halide salt by interaction with part of the hydrohalide acid already in the cellulose. If no hydrohalide acid be required in the esterification, the residual acid in the cellulose after the pretreatment may be employed to form the required halide catalysts in situ. For example by adding ferric oxide or ferric ace tate or the like to a cellulosic material pretreated with hydrochloric acid, ferric chlo ride for use as a catalyst may be formed within the cellulosic material. It is to be noted however that even in the case of acetylating or esterifying according to the processes of these prior applications, the present invention is not limited to the non removal of the hydrohalide acid.

The acetylation or other esteriiication may be conducted in presence of a solvent for the cellulose ester produced or in presence of a non-solvent diluent or in the absence of solvents or diluents by employing a vaporous esterifying agent.

The following examples illustrate the processes of pretreatment according to the present invention and the prefer-rec methods of subsequent esterification, but they are not to be considered as limiting the invention in any way.

Ewamp Z5 1 parts of cotton cellulose are sprayed with 15 to 30 parts of concentrated hydrochloric acid (about 33% strength) and allowed to stand with occasional turning for 2 to 3 hours at normal ten'iperature. The pretreated material is then introuuced in the acetylator into amixture of 800 parts of acetic acid, 300 parts of acetic anhydride and 15 parts of ferric chloride. The acetylation is carried out in the cold with constant mixing or stirring. A clear solution of cellulose acetate of high viscosity is obtained.

E trample 2 Example 3 100 parts of cotton cellulose are introduced in an acetylator into a mixture of 600 parts of acetic acid and 30 parts of hydrochloric acid and allowed to stand with stirring for 3 to 7 hours. hereafter there are added 10 parts of stannic chloride and 600 parts of acetic anhydride and the mass is constantly stirred throughout the reaction which is carried out at about normal temperature. lhe acetylation proceeds smoothly and a. clear solution is obtained.

The cellulose acetates or cellulose esters obtaincd may be used in their estcrilication solutions (more particularly when the esteriiicati is carried out accor lg to the prior applications referred to) or in solutions of the primary estcriiication products for the pro- "l silks, iilnis etc. or they to secondary treatments tions for the purpose of changing their dies i. e. the. so-called ripening. The rca'tinents or ripening may be 1 iuiary esterification soluoss, prefer ably without neuhydrochloric or other hydrohalide acid if pres and preferably without eliminatim; any halide catalyst if used and arter de #31? any remain- Q it ner t a 1. ion of water or other illlllJtlllCl de roying agents, such for L nee as hydroxyl derivatives, oxy acids, for instance lactic acid, alcohols etc. It no acid catalyst be used in the esteritication, hydrochloric .r other hydrohalide acid may, it c esired, be added to a *celerate the reaction. ernatively, the esters either precipitated from. the prim sterification solutions or 4.

we obtained other than in solution may be .xsolved or suspended a d then subjected to SQCOllClclY treatments or ripening. The secondary treatments or reactions may be carrie 1 out with or without addition of innic acids, acid salts or other i or promoting the secondary treatment or action, the treatn'ient in any being stopped when the required solubility been reached. It is particularly advantageous to conduct the further treatments or reactions in the joint presence of hydrohalide acid an metal halide or other cataysts used accoi lin to the prior applications *eferred to, either in the primitive esteriiicaon solu ous or suspensions or after separarem. For the ripening or further L do -s or reactions one should r'ii t any remaining acetic anhydride or estcri ing anhydride that may remain in the esterification solution or suspension or in the primary ester, by adding water or other anhydride destroying agents to the estcrilication solution or to the solutions or su ensions oi the primary ester.

lie the ripening or secondary or further tr ati'ucnts ot the nrimary esterification products may with advantage be conducted at. ordinary or moderate temperatures, one may if desired quicken the reaction by heating up to relative nigh or high temperatures even up to 80 or 100 C. or higher, but in such cases the presence of free mineral acids is preferably avoided.

ii The secondary or further treatments of the primary esterification products will be stopped when the particular solubility de-' sired is reached.

In carrying out the esterification with halide catalysts according to the methods described in my said prior applications and the secondary treatments or ripening according to the preferred methods described therein, it will be seen that very considerable advantages accrue, since a continuous series of processes is possible without any separation of reagents at intermediate stages. For example a cellulosic material may be. pretreated with 10% of its weight of hydroohloric acid (calculated as H01) in aqueous solution, a quantity of ferric chloride equal to (say) 510% of the weight of the cellulosic material added together with acetic anhydride and acetic acid and finally, after the acct lation, a secondary reaction or ripening carried out directly in presence of the hydrochloric acid and ferric chloride.

The cellulose acetates or other esters can be employed in their primary esterification solutions in their different stages or phases of acetylation, for the production of artificial silks and the like, films, celluloid-substitutes or other thermoplastic masses, moulding powders or articles, etc.

Further the invention permits of obtaining cellulose esters of high quality which are soluble in acetone or in very low boiling solvents, for instance methyl forinate, acetaldehyde, formaldehyde etc. Also suitable high boiling solvents or plasticizing or softening agents can be readily incorporated with them or their solutions in volatile solvent-s and/or very low boiling solvents.

The cellulose acetates or other esters, either in their primary estcrification solutions and with or Without secondary treat-- tration containing over 20% e. g. 25-80% or more.

The term disintegration is employed'in the specification and claims as connoting loss of structure.

What I claim and desire to secure b Letters Patent is 1. Process for the treatment of material consisting substantially of cellulose without substantial disintegration, comprising treating the material with up to 50% of its weight of hydrogen halide under conditions to avoid substantial disintegration of the cellulose, whereby it is rendered more reactive to esterification.

2. Process for the treatment of material consisting substantially oi": cellulose without substantial disintegration, comprising treating the material with up to 50% of its weight of hydrogen chloride under such conditions to avoid substantial disintegration of the cellulose, whereby it is rendered more reactive to esterification.

3. Process for the treatment of material consisting substantially of cellulose without substantial disintegration, comprising treat ing the material with up to 50% of its weight of hydrogen halide in aqueous solution under such conditions to avoid substantial disintegration ofthe cellulose, whereby it is rendered more reactive to esteriiication.

4:. Process for the treatment of material consisting substantially of cellulose without substantial disintegration, comprising treating the material with up to 50% of its weight of hydrogen chloride in aqueous solution under such conditions to avoid substantial disintegration of the cellulose, whereby it rendered more reactive to esterification.

5. Process for the treatment oi? material consisting substantially of cellulose without substantial disintegration, comprising treating the material at normal temperature, with up to 50% of its weight or" hydrogen chloride under such conditions to avoid substantial disintegration of the cellulose, whereby it is rendered more reactive to esteriiicai'ion.

0. Process for the treatment oi material consisting substantially oi cellulose without substantial disintegration, comprising treating the material at normal temperature, with up to 50% of its weight of hydrogen chloride .in aqueous solution under such conditions to avoid substantial disintegration of We cellulose, whereby it is rendered more reactive to esteritication.

7. Process for the treatment of material consisting substantially of cellulose without substantial disintegration, comprising treat ing the material with organic acid and with up to 50% of its weight of hydrogen halide under such conditions to avoid substantial disintegration of the cellulose, wherebyit is rendered more reactive to esterilicatiou.

8. Process for the treatment or" material consisting substantialy of cellulose without substantial disintegration, comprising treating the material with acetic acic. and with up to 50% of its weight of hydrogen chloride in aqueous solution under such conditions to avoid suhsiantial disintegration of the cellulose, whereby it is rendered more reactive to esterificat-ion.

9. Process for the treatment of material consisting substantially oi cellulose without substantial disintegration, comprising treating the material with up to 50% of its weight of hydrogen halide under such conditions to avoid substantial disintegration of the cellulose, and thereafter esterifying it.

10. Process for the treatment of cellulosic material, comprising treating the material with up to 50% of its weight of hydrogen chloride without substantial disintegration and hereafter acetylating with acetic anhydride.

11. Process for the treatment of material consisting substantially of cellulose, comprising treating the material with up to 50% of its weight of hydrogen chloride in aque ous solution without substantial disintegration, and thereafter acetylating with acetic anhydride in presence of halide catalysts.

12. Process for the treatment of material cor. isting substantially of cellulose, comprising treating the material. with acetic acid and with up to 530% of its weight of hydrogen chloride in aqueous solution without sul stantial disintegration and thereafter acetylating with acetic anhydride in presence of halide catalysts.

13. Process for the treatment of material. consisting substantially oi cellulose without substantial disintegration comprising treating the maial with ower fatty acid and with up to 50% oi its weight of hydrogen halide at suhstaniially normal temperatures whereby it is rendered more reactive to esteriiication.

Lil. Process for the treatment of material consisting substantially of cellulose without substantial disintegration, comprising treating the material with acetic acid and with up to 50% oil its weight of hydrogen chloride in aqueous solution at substantially normal temp ratures, whereby it is rendered more reactive to esterilicationi 15. Process for the treatment of material consisting substantially of cellulose without substantial disintegration, comprising treating the material with up to 50% of its Weight of hydrogen halide at substantially normal temperatures and thereafter esteritying it.

16. Process for the treatmentof material consisting substantially of cellulose compr1sing tre "ing the material with up to 50% of its weig it of hydrogen chloride at substantially normal temperatures without substanlial disintegration, and thereafter acetylat ing it with acetic anhydride.

1?. Process for the treatmentof material consisting substantially of cellulose, comprising treating the material with acetic acid and with up to 50% of its weight of hydrogen chloride in aqueous solution at substantially normal temperatures \Vii hout substantial disintegration and thereafter acetylating with acetic anhydride in the presence of halide catalysts.

In testimony whereof I have hereunto subscribed my name.

HENRY DREYFUS. 

